Windows 10 OpenSSH authorized keys error with sshd

Question

after a lot of support from reading the great posts here my first question:

I try to set up ssh with keys between a Mac and Windows 10 (20H2). What I did until now:

• generated keys on Mac, tested pub key with auto log onto raspberry, all fine.
• copied the pub keys to the win10, set up the access right according to https://askme4tech.com/how-install-and-configure-open-ssh-server-windows-10
• change the sshd_config to this
• if I try to ssh the win10, I get (with ssh -v) (only the last lines):

...
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.2.157 ([192.168.2.157]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
client_loop: send disconnect: Broken pipe

• in case I stop the sshd on Win10 and start it not as a service, just with c:\>sshd.exe everything works fine. I found this out when starting the debug mode sshd -d manually.

• Due to my limited know how on Win10 I do not have any more ideas where to look or fix this, so thanks for some hints!

Manu

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

#HostKey __PROGRAMDATA__/ssh/ssh_host_rsa_key
#HostKey __PROGRAMDATA__/ssh/ssh_host_dsa_key
#HostKey __PROGRAMDATA__/ssh/ssh_host_ecdsa_key
#HostKey __PROGRAMDATA__/ssh/ssh_host_ed25519_key

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

PubkeyAuthentication yes

# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile  .ssh/authorized_keys

#AuthorizedPrincipalsFile none

# For this to work you will also need host keys in %programData%/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#PermitUserEnvironment no
ClientAliveInterval 60
#ClientAliveCountMax 3
#UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# override default of no subsystems
Subsystem   sftp    sftp-server.exe

# Example of overriding settings on a per-user basis
#Match User anoncvs
#   AllowTcpForwarding no
#   PermitTTY no
#   ForceCommand cvs server

#Match Group administrators
#      AuthorizedKeysFile __PROGRAMDATA__/ssh/administrators_authorized_keys

Answer 1

in case I stop the sshd on Win10 and start it not as a service, just with c:>sshd.exe

• In one case, sshd is run as a service, possibly with the LocalSystem account
• In the other, from comand-line, you are running sshd as you (your Windows account).

The environment would not be the same, especially for the "authorized_keys" file.
As mentioned in the documentation:

In Windows, sshd reads configuration data from %programdata%\ssh\sshd_config by default, or a different configuration file may be specified by launching sshd.exe with the -f parameter.
If the file is absent, sshd generates one with the default configuration when the service is started.

Activate the logs when running the ssh daemon as a Windows service, as seen here:

Open an admin powershell prompt and run:

notepad C:\ProgramData\ssh\sshd_config

Find the "# Logging" section and add in these 2 lines.

SyslogFacility LOCAL0
LogLevel DEBUG3

Run services.msc and restart the service if its running, or start it if it's stopped.
Make sure it is set to run as the system account.